Method, apparatus, and system for transmitting and receiving information of an uncoded channel in an orthogonal frequency division multiplexing system

ABSTRACT

A method apparatus and system for efficiently transmitting and receiving channels are provided in a wireless communication system based on Orthogonal Frequency Division Multiplexing (OFDM). A multiplexing scheme differs according to a channel when a transmitter transmits a packet data channel, a common control channel and a control channel designated for a particular user. Uncoded 1-bit information is broadly dispersed in frequency and time domains using multiplexing technology for maximizing diversity gain in a channel for transmitting information of at least one bit to a particular user like an acknowledgement (ACK) channel. The transmitter converts a sequence obtained by multiplexing multiple bits to be transmitted to a plurality of users to parallel signals, and broadly disperses the parallel signals in the time and frequency domains. When the uncoded 1-bit information is transmitted, reception reliability is improved because channel coding and transmission are efficiently performed using a small amount of resources.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of a prior applicationSer. No. 15/230,922, filed on Aug. 8, 2016, and will issue as U.S. Pat.No. 9,774,435 on Sep. 26, 2017, which is a continuation application of aprior application Ser. No. 14/011,314, filed on Aug. 27, 2013, whichissued as U.S. Pat. No. 9,413,510 on Aug. 9, 2016, which is acontinuation application of a prior application Ser. No. 11/417,217,filed on May 4, 2006, which issued as U.S. Pat. No. 8,520,499 on Aug.27, 2013, and which claims the benefit of Korean Patent Application No.10-2005-0037777, filed on May 4, 2005, in the Korean IntellectualProperty Office, the entire disclosure of which is hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention generally relates to a method and apparatus fortransmitting and receiving data in a wireless communication system basedon Orthogonal Frequency Division Multiplexing (OFDM). More particularly,the present invention relates to a method and apparatus for efficientlytransmitting and receiving channel data for which a coding process isnot required.

Description of the Related Art

Recently, a large amount of research is being conducted on an OrthogonalFrequency Division Multiplexing (OFDM) transmission method serving as ascheme useful for high-speed data transmission using a radio channel ina mobile communication system. The OFDM scheme is a type ofMulti-Carrier Modulation (MCM) scheme for converting a serially inputsymbol stream in parallel and then modulating and transmitting parallelsignals through a plurality of orthogonal subcarriers, in other words aplurality of subcarrier channels. The OFDM transmission scheme copies asecond half part of an OFDM symbol, attaches the copied part as a CyclicPrefix (CP) before the OFDM symbol, and transmits the OFDM symbol,thereby removing InterSymbol Interference (ISI) from a previous symbol.The OFDM transmission scheme, robust to a multipath fading channel, issuitable for broadband high-speed communication.

FIG. 1 is a block diagram illustrating a structure of a conventionaltransmitter in a wireless communication system based on OFDM.

Referring to FIG. 1, a channel encoder 101 receives a predeterminedinformation bit stream and then performs a channel coding process forthe received information bit stream. Conventionally, the channel encoder101 can use a convolutional encoder, a turbo encoder, a Low DensityParity Check (LDPC) encoder, and so on. The encoded information bitstream from the channel encoder 101 is input to a modulator 103. Themodulator 103 modulates the encoded information bit stream in apredefined modulation scheme such as Quadrature Phase Shift Keying(QPSK), 8-Phase Shift Keying (8PSK), 16-Quadrature Amplitude Modulation(16QAM), and so on. It is obvious that a rate matcher (not illustrated)for performing repetition and puncturing functions and so on may beadditionally inserted between the channel encoder 101 and the modulator103.

A Serial to Parallel Converter (SPC) converts an output signal of themodulator 103 to parallel signals, and then inputs the parallel signalsto an Inverse Fast Fourier Transform (IFFT) processor 107. The IFFTprocessor 107 transforms the parallel signals according to an IFFT. AParallel to Serial Converter (PSC) 109 converts the transformed parallelsignals to a serial signal. A CP inserter 111 inserts a CP forpreventing interference into the serial signal (or symbol), and thenoutputs the symbol with the CP. An OFDM symbol stream into which the CPhas been inserted is transmitted to a wireless network through a RadioFrequency (RF) processor 113 and an antenna 115.

When the above-described conventional OFDM transmitter performs atransmission operation, a modified multiplexing scheme performs aHadamard transform on modulated symbols to be transmitted from the OFDMtransmitter in a frequency domain and transmits the transformed symbolswithout directly transmitting one modulated symbol through onesubcarrier. This scheme is referred to as Multi-Carrier Code DivisionMultiplexing (MC-CDM) or Orthogonal Frequency Code Division Multiplexing(OFCDM). Hereinafter, MC-CDM and OFCDM are referred to as the OFCDMscheme.

FIG. 2 is a block diagram illustrating a structure of a conventionalOFCDM transmitter in the wireless communication system based on OFDM.The OFCDM transmitter of FIG. 2 is configured by adding a well-knownHadamard transform processor 210 to the OFDM transmitter of FIG. 1 suchthat a CDM transmission scheme is applied to the OFDM transmissionscheme.

Referring to FIG. 2, a channel encoder 201 receives a predeterminedinformation bit stream and performs a conventional channel codingprocess such as convolutional coding, turbo coding, Low Density ParityCheck (LDPC) coding, and so on. The encoded information bit stream fromthe channel encoder 201 is input to a modulator 203. The modulator 203modulates the encoded information bit stream in a predefined modulationscheme. A Demultiplexer (DEMUX) 205 of the Hadamard transform processor210 demultiplexes the modulated signal (or symbol stream) into Noutputs. A plurality of covers with Walsh functions, in other wordsWalsh covers 0˜N, 207 cover the N output signals with predefined Walshcodes. An adder 209 computes a sum of the signals covered with the Walshcodes, and outputs the signal sum to an SPC 211. An output of the SPC211 is transmitted to a wireless network through an IFFT processor 213,a PSC 215, a CP inserter 217, an RF processor 219, and an antenna 221.

In the above-mentioned two multiplexing transmission techniques, inother words the OFDM and OFCDM schemes, one scheme does not alwaysoutperform the other scheme. Relative performances of the OFDM and OFCDMschemes can differ according to many factors. The main factors capableof varying the performances of the OFDM and OFCDM schemes are the coderate of transmitted data, channel frequency selectivity, and so on. Asdescribed above, simulation results of a performance comparison betweenthe OFDM and OFCDM schemes according to a code rate, channel frequencyselectivity, and so on are illustrated in FIGS. 3 to 5. In FIGS. 3 to 5,the horizontal axis represents a signal to noise ratio (Eb/Nt) whentransmitted data is received, the vertical axis represents a PacketError Rate (PER), EG represents equal gain paths, and UEG representsunequal gain paths.

FIGS. 3 to 5 illustrate results of a performance comparison between theOFDM and OFCDM schemes, for example, when code rates of transmitted dataare ¼, ½, and ⅘, respectively. It can be seen that the OFDM schemeoutperforms an OFCDM (or MC-CDM) scheme when the code rates oftransmitted data are low (¼ and ½) as illustrated in FIGS. 3 and 4.Moreover, it can be seen that a performance differs according to thenumber of equal/unequal gain paths even when frequency selectivity isvaried. As illustrated in FIG. 5, it can be seen that the OFCDM schemeoutperforms the OFDM scheme when the code rate of transmitted data ishigh (⅘).

Because performance differs according to a code rate or coding of atransmitted channel in the wireless communication system based on OFDM,there exists a need for a method apparatus, and system for efficientlytransmitting data while considering this difference.

SUMMARY OF THE INVENTION

It is, therefore, an exemplary object of the present invention toprovide a method, apparatus, and system for transmitting and receivinguncoded information in an Orthogonal Frequency Division Multiplexing(OFDM) system for transmitting various control information using a radiochannel.

It is another exemplary object of the present invention to provide amethod, apparatus, and system for transmitting and receiving 1-bitinformation in an Orthogonal Frequency Division Multiplexing (OFDM)system for transmitting various control information using a radiochannel.

It is another exemplary object of the present invention to provide atransmission/reception method, apparatus, and system that can improvediversity gain when 1-bit information is transmitted to a plurality ofusers in an Orthogonal Frequency Division Multiplexing (OFDM) system fortransmitting various control information using a radio channel.

It is yet another exemplary object of the present invention to provide amethod, apparatus, and system for transmitting and receiving uncodedcontrol information in an Orthogonal Frequency Division Multiplexing(OFDM) system in which various control information is transmitted usinga radio channel and a multiplexing scheme differs according to a channeltype.

In accordance with an exemplary aspect of the present invention, thereis provided a method for transmitting information of an uncoded channelfrom a base station in an Orthogonal Frequency Division Multiplexing(OFDM) system, comprising the steps of performing a unitary transform onthe uncoded channel information, mapping subcarriers in a pattern forincreasing diversity gain of the information on which the unitarytransform has been performed, and multiplexing and transmitting otherchannel information with the information mapped to the subcarriers.

In accordance with another exemplary aspect of the present invention,there is provided an apparatus for transmitting information of anuncoded channel in a base station of an Orthogonal Frequency DivisionMultiplexing (OFDM) system, comprising, a unitary transform processorfor performing a unitary transform on the uncoded channel information, asubcarrier mapper for mapping subcarriers in a pattern for increasingdiversity gain of the information on which the unitary transform hasbeen performed according to a predetermined control signal, amultiplexer for multiplexing and transmitting other channel informationwith the information mapped to the subcarriers and a controller forcontrolling an operation of the subcarrier mapper.

In accordance with another exemplary aspect of the present invention,there is provided a method for receiving information of an uncodedchannel in a terminal of an Orthogonal Frequency Division Multiplexing(OFDM) system, comprising the steps of: receiving the uncoded channelinformation from a radio channel and performing an inverse unitarytransform on the received uncoded channel information.

In accordance with another exemplary aspect of the present invention,there is provided an apparatus for receiving information of an uncodedchannel in a terminal of an Orthogonal Frequency Division Multiplexing(OFDM) system, comprising a reception module for receiving the uncodedchannel information from a radio channel, an inverse unitary transformprocessor for performing an inverse unitary transform on the receiveduncoded channel information and a controller for controlling anoperation of the inverse unitary transform processor.

In accordance with yet another exemplary aspect of the presentinvention, there is provided an Orthogonal Frequency DivisionMultiplexing (OFDM) system for transmitting and receiving information ofan uncoded channel, comprising a transmitter for performing a unitarytransform on the uncoded channel information, mapping subcarriers in apattern for increasing diversity gain of the information on which theunitary transform has been performed, and multiplexing and transmittingother channel information with the information mapped to thesubcarriers, and a receiver for demultiplexing information received froma radio channel to a designated reception path, receiving the uncodedchannel information of the radio channel, and performing an inverseunitary transform on the uncoded channel information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and aspects of the present invention will bemore clearly understood from the following detailed description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating a structure of a conventionaltransmitter in a wireless communication system based on OrthogonalFrequency Division Multiplexing (OFDM);

FIG. 2 is a block diagram illustrating a structure of a conventionalOrthogonal Frequency Code Division Multiplexing (OFCDM) transmitter inthe wireless communication system based on OFDM;

FIGS. 3 to 5 illustrate simulation results of a performance comparisonbetween the OFDM and OFCDM schemes;

FIG. 6 illustrates simulation results of reception reliability whenuncoded 1-bit information is transmitted to a particular user in thewireless communication system based on the OFDM or OFCDM scheme;

FIG. 7 is a flowchart illustrating a method for transmitting uncodedinformation in an OFDM system in accordance with an exemplary embodimentof the present invention;

FIG. 8 is a block diagram illustrating a structure of an apparatus fortransmitting uncoded information in the OFDM system in accordance withan exemplary embodiment of the present invention;

FIG. 9 is a block diagram illustrating a structure of an apparatus fortransmitting uncoded information in the OFDM system in accordance withanother exemplary embodiment of the present invention;

FIGS. 10A and 10B illustrate an example of mapped subcarriers inaccordance with an exemplary embodiment of the present invention;

FIG. 11 is a block diagram illustrating a structure of an apparatus forreceiving uncoded information in the OFDM system in accordance with anexemplary embodiment of the present invention;

FIG. 12 is a flowchart illustrating a method for receiving uncodedinformation in accordance with an exemplary embodiment of the presentinvention; and

FIG. 13 is a flowchart illustrating a channel allocation process and asystem parameter setting process when uncoded information is transmittedin the OFDM system in accordance with an exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention will be described indetail herein below with reference to the accompanying drawings. In thefollowing description, detailed descriptions of functions andconfigurations incorporated herein that are well known to those skilledin the art are omitted for clarity and conciseness.

Before exemplary embodiments of the present invention are described, anexemplary concept of the present invention will be briefly described.

When different types of channels, for example, a packet data channel, acommon control channel, and a control channel designated for aparticular user, are configured in a wireless communication system,reception performance may be degraded according to a transmission schemeif only a particular multiplexing scheme is used. This receptionperformance degradation may occur when information of at least one bitis transmitted in a channel for transmittingAcknowledgement/Non-acknowledgement (ACK/NACK) information to aparticular user and a channel for transmitting a power control bit orwhen uncoded information is transmitted. Conventionally, 1-bit controlinformation is transmitted as the uncoded information.

That is, FIG. 6 illustrates simulation results of reception reliabilitywhen uncoded 1-bit information is transmitted to a particular user in awireless communication system using an Orthogonal Frequency DivisionMultiplexing (OFDM) or Orthogonal Frequency Code Division Multiplexing(OFCDM) scheme. In the simulation results of FIGS. 3 to 5, it can beseen that the relative reception performance superiority between theOFDM and OFCDM schemes differs according to a code rate. Moreover, itcan be seen that the performance of the OFCDM scheme is superior when acode rate of a transmission packet is high in a data channel and theperformance of the OFDM scheme is superior when a code rate of atransmission packet is low in the data channel. Moreover, it can be seenthat the reception performance of the OFCDM scheme is superior whenuncoded 1-bit information is transmitted at an uncoded Bit Error Rate(BER) as illustrated in FIG. 6.

Exemplary embodiments of the present invention propose technology fortransmitting and receiving information by broadly dispersing 1-bitinformation to be transmitted to a plurality of users in frequency andtime domains using a unitary transform technique such as a Hadamardtransform or Fast Fourier Transform (FFT) such that diversity gain canbe maximized when the 1-bit information and/or uncoded information aretransmitted to a particular user.

For convenience, an ACK channel corresponding to a channel fortransmitting uncoded 1-bit information in accordance with an exemplaryembodiment of the present invention will be described in detail. One ofordinary skill in the art will appreciate that thetransmission/reception method and apparatus of the present inventiondescribed below can be applied to other channels for transmitting 1 bitto a particular user that are similar to the ACK channel or an uncodedchannel (for example, a channel for transmitting a power control bit).

FIG. 7 is a flowchart illustrating a method for transmitting uncodedinformation in an OFDM system in accordance with an exemplary embodimentof the present invention.

Using the transmission method of an exemplary embodiment of the presentinvention, a base station determines whether an associated channel is acoded channel or an uncoded channel when information of each channel istransmitted in step 701. If the associated channel is an uncoded channelsuch as an ACK channel as a result of the determination in step 701, thebase station performs a unitary transform on information of 1-bits to betransmitted to a plurality of users using a Hadamard transform or FFTtechnique in step 703. After the information of 1-bits on which theunitary transform has been performed is mapped to subcarriers such thatthe maximum diversity gain can be obtained in step 705, they aremultiplexed with other channel information and are dispersed in the timeand frequency domains in step 707. On the other hand, if it isdetermined in step 701 that the associated channel is the coded channel,information of the associated channel is transmitted in the OFDM schemeusing the transmitter structure as illustrated in FIG. 1. Information tobe transmitted in the OFDM scheme may be information of a controlchannel carrying control information to be commonly transmitted to theusers or information of a data channel with characteristics differentfrom those of the ACK channel.

FIG. 13 is a flowchart illustrating a channel allocation process and asystem parameter setting process when uncoded information is transmittedin the OFDM system in accordance with an exemplary embodiment of thepresent invention. As an example of the uncoded information, an ACK/NACKbit will be described.

In step 1301 of FIG. 13, a base station controls a subcarrier mapperwithin a transmitter described below such that one ACK channel is mappedto subcarriers within one transmission unit in the time and frequencydomains. In step 1303, the base station sets a system parameter of theACK channel according to a type of a used unitary transform processor.For example, when a Hadamard transform processor is used as the unitarytransform processor, a spreading factor (SF_ACKCH) is set as the systemparameter. When an FFT processor is used, an FFT size is set as thesystem parameter. Subsequently, the base station allocates an ACKchannel index for each terminal at a call setup time in step 1305. Atthis time, when the Hadamard transform processor is used as the unitarytransform processor, a Walsh code index is allocated to each terminal.When the FFT processor is used as the unitary transform processor, anFFT input position for each terminal is allocated.

Subsequently, the base station determines whether the number ofterminals located within an associated region exceeds a system parametervalue in step 1307. If the number of terminals exceeds the spreadingfactor or the FFT size, the base station proceeds to step 1309 toadditionally allocate an ACK channel. Herein, the additional ACK channelallocation is performed whenever the number of terminals exceeds thesystem parameter value. For example, when the spreading factor(SF_ACKCH) is 16, the number of terminals for which one channel can besupported is 16. If the number of terminals is more than 16, it meansthat another ACK channel is to be allocated. In step 1311, the basestation transmits an ACK/NACK bit to each terminal through the ACKchannel allocated as described above.

FIG. 8 is a block diagram illustrating a structure of an apparatus fortransmitting uncoded information in the OFDM system in accordance withan exemplary embodiment of the present invention. This apparatus isprovided in a base station or the like.

In FIG. 8, Walsh covers 801 receive ACK/NACK bits to be transmitted tomultiple users #1˜#N and cover (or spread) the received ACK/NACK bitswith Walsh codes (or Walsh functions) allocated thereto. The Walsh codes(or Walsh functions) may use codes agreed to between the base stationand user terminals using L3 signaling or the like. An adder 803 computesa sum of the ACK/NACK bits covered with the Walsh codes, and inputs theACK/NACK bit sum to a subcarrier mapper 807. The Walsh covers 801 andthe adder 803 configure a Hadamard transform processor 805 forperforming a unitary transform.

Under control of a controller 808, the subcarrier mapper 807 maps theACK/NACK bits to subcarriers such that the maximum diversity gain can beobtained. For example, the subcarrier mapper 807 performs the mappingprocess such that the subcarriers are dispersed on the time andfrequency axes as illustrated in FIG. 10A. The controller 808 controlsthe system parameter setting process and the channel allocation processfor an ACK/NACK bit transmission as described with reference to FIG. 13.

FIG. 10A illustrates an example of the mapped subcarriers 11 in shadedregions. The subcarriers mapped as illustrated in FIG. 10A are dispersedto transmit the ACK/NACK bits such that the maximum diversity gain canbe obtained on the time and frequency axes. It is to be noted that thesubcarrier mapper 807 operates in a unit of multiple OFDM symbols ratherthan one OFDM symbol. In one example, a pattern of one ACKCH #1illustrated in FIG. 10A, in other words frequency and time positions ofsubcarriers in one transmission unit, can be predefined through the ACKchannel index as described with reference to FIG. 13 and can be agreedbetween the base station and the terminals. In the event that thesubcarrier allocation pattern configures one ACK channel as illustratedin FIG. 10A, a different subcarrier allocation pattern for anadditionally allocated ACK channel is distinguished and indicated by theACK channel index as described with reference to FIG. 13.

A Multiplexer (MUX) 815 multiplexes an output of the subcarrier mapper807 with information of other control channels and then outputs amultiplexing result. Herein, the other control channels are controlchannels with characteristics different from those of the ACK channel,for example uncoded channels or coded channels for transmitting controlinformation of multiple bits rather than one bit. A transmission of theother control channels conforms to the OFDM transmission scheme asdescribed with reference to FIG. 1. A channel encoder 809, a modulator811, and an SPC 813 of FIG. 8 are used to transmit the other controlchannel information.

That is, the channel encoder 809 encodes the other control channelinformation (or channel information of multiple bits). The modulator 811modulates the encoded information. The SPC 813 converts the modulatedinformation to parallel signals. The parallel signals are multiplexedalong with an output of the subcarrier mapper 807. A multiplexing resultis input to an Inverse Fast Fourier Transform (IFFT) processor 817. IFFTsignals are converted to a serial signal in a PSC (not illustrated). ACP inserter 819 inserts a CP for preventing interference into the serialsignal, and transmits the signal into which the CP has been inserted toa wireless network through an RF processor 821 and an antenna 823.

FIG. 9 is a block diagram illustrating a structure of an apparatus fortransmitting uncoded information in the OFDM system in accordance withanother exemplary embodiment of the present invention. This apparatus isprovided in a base station and the like. Because the remainingcomponents 903˜919 except an FFT processor 901 in the structure of FIG.9 perform the same operations as those of FIG. 8, their description isomitted.

The exemplary embodiment of FIG. 9 uses the FFT processor 901 in theplace of the Hadamard transform processor 805 of FIG. 8 for performingthe unitary transform. Accordingly, ACK/MACK bits of multiple users#1˜#N on which the unitary transform has been performed through the FFTprocessor 901 are mapped to subcarriers. The MUX 911 multiplexes theACK/NACK bits with information of other control channels fortransferring channel information of multiple bits, such that the channelinformation is transmitted to a wireless network.

The exemplary embodiments of FIGS. 8 and 9 use the unitary transformprocessors such as the Hadamard transform processor 805 and the FFTprocessor 901. Also, there can be used transform processors withquasi-unitary characteristics, in other words transform processors inwhich multiple sets are provided, elements of the same set areorthogonal to each other, and cross talk is minimized between elementsof different sets.

In the exemplary embodiments of FIGS. 8 and 9, the subcarrier mappers807 and 903 map subcarriers as illustrated in FIG. 10A such thatdiversity gain of the ACK/NACK bits on which the unitary transform hasbeen performed can be maximized. Also, the subcarriers can be mappedsuch that high diversity gain is obtained as illustrated in FIG. 10B. Itcan be useful that a diversity is obtained in a particular subband 13 asillustrated in FIG. 10B when a terminal prefers a particular subband, inother words a base station transmitter knows that a channel state of theparticular subband is good and channel states of the remaining subbandsare bad.

Next, a receiver of an exemplary embodiment of the present inventionwill be described with reference to FIGS. 11 and 12. For convenience, anoperation for receiving ACK/NACK bits will be described also in anexemplary embodiment of the receiver.

FIG. 11 is a block diagram illustrating a structure of an apparatus forreceiving uncoded information in the OFDM system in accordance with anexemplary embodiment of the present invention. This apparatus isprovided in a user terminal and so on.

In the receiver structure of FIG. 11, the remaining components 1101 1109and 1113˜1117 except a Demultiplexer (DEMUX) 1111, a unitary transformprocessor 1119, and a controller 1121 have the same configurations asthose of a conventional OFDM receiver. In FIG. 11, an OFDM symbolreceived through the antenna 1101 and the RF processor 1103 includesACK/NACK bits. The CP remover 1105 removes a CP from the received OFDMsymbol. The SPC 1107 converts a signal from which the CP has beenremoved to parallel signals. The parallel signals are input to the FFTprocessor 1109. The DEMUX 1111 demultiplexes an output of the FFTprocessor 1109 according to a type of received channel, and outputs ademultiplexing result to a predefined path.

For channels for transferring control information of multiple bits, areception path is set to a first path connected to the PSC 1113. Thechannels are demodulated and decoded according to the conventional OFDMreception operation. For channels for transferring uncoded 1-bitinformation such as an ACK/NACK bit, a reception path is set to a secondpath connected to the unitary transform processor 1119. Under control ofthe controller 1121, the channels undergo an inverse Hadamard transformor IFFT, such that the ACK/NACK bit and the like are output.

When an inverse Hadamard transform processor is used as the inverseunitary transform processor 1119, it can be implemented with, forexample, a component for performing Walsh decovering. In this case, thecontroller 1121 performs a control operation such that a Walsh decovercan operate using a Walsh code allocated to an associated terminal.

FIG. 12 is a flowchart illustrating a method for receiving uncodedinformation in accordance with an exemplary embodiment of the presentinvention. This method indicates a reception operation of a terminal andso on.

When the terminal receives information of a particular channel through awireless network in step 1201, the DEMUX 1111 demultiplexes the receivedchannel information to a predefined path according to a type of receivedchannel in step 1203. Upon determining that the received channel is achannel for transmitting uncoded information such as an ACK/NACK bit instep 1205, the terminal performs an inverse unitary transform on thereceived information and outputs the transformed information in step1207. Upon determining that the received channel is a coded channel fortransmitting multiple bits in step 1205, the terminal processes thereceived information according to an OFDM reception operation in step1209.

As is apparent from the above description, exemplary embodiments of thepresent invention can improve reception reliability of associatedchannels by providing an efficient transmission/reception method andapparatus when uncoded information or 1-bit information is transmittedto a user through a radio channel in a wireless communication systembased on OFDM.

Moreover, exemplary embodiments of the present invention can improvediversity gain when 1-bit control information is transmitted to aplurality of users in an OFDM system.

Although exemplary embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions, and substitutions arepossible, without departing from the scope of the present invention.Therefore, the present invention is not limited to the above-describedembodiments, but is defined by the following claims, along with theirfull scope of equivalents.

What is claimed is:
 1. A method for transmitting control information bya base station in an orthogonal frequency division multiplexing (OFDM)system, the method comprising: spreading, by the base station,acknowledgement (ACK) information by applying a code from a set ofcodes; mapping, by the base station, the spread ACK information tosubcarriers in a pattern for increasing diversity gain of the spread ACKinformation; encoding, by the base station, other control informationbased on a channel encoding scheme without spreading; multiplexing, bythe base station, the spread ACK information mapped to the subcarriersand the encoded other control information; and transmitting themultiplexed information to at least one terminal.
 2. The method of claim1, wherein the spread ACK information is mapped based on an ACK channelindex.
 3. The method of claim 1, wherein the spread ACK information ismapped to a plurality of OFDM symbols.
 4. The method of claim 1, whereinthe ACK information is spread using a spreading factor.
 5. The method ofclaim 1, further comprising: allocating an ACK channel corresponding tothe ACK information based on a spreading factor or a fast fouriertransform (FFT) size.
 6. The method of claim 5, wherein the ACK channelis allocated when a number of terminals within a region of the basestation exceeds the spreading factor or the FFT size.
 7. The method ofclaim 1, wherein the mapping of the subcarriers comprises mapping thesubcarriers in a particular subband.
 8. A base station for transmittingcontrol information in an orthogonal frequency division multiplexing(OFDM) system, the base station comprising: a controller configured to:spread acknowledgement (ACK) information by applying a code from a setof codes, map the spread ACK information to subcarriers in a pattern forincreasing diversity gain of the spread ACK information, encode othercontrol information based on a channel encoding scheme withoutspreading, and multiplex the spread ACK information mapped to thesubcarriers and the encoded other control information; and a transceivercoupled with the controller and configured to transmit the multiplexedinformation to at least one terminal.
 9. The base station of claim 8,wherein the spread ACK information is mapped based on an ACK channelindex.
 10. The base station of claim 8, wherein the spread ACKinformation is mapped to a plurality of OFDM symbols.
 11. The basestation of claim 8, wherein the ACK information is spread using aspreading factor.
 12. The base station of claim 8, wherein thecontroller is further configured to allocate an ACK channelcorresponding to the ACK information based on a spreading factor or afast fourier transform (FFT) size.
 13. The base station of claim 12,wherein the ACK channel is allocated when a number of terminals within aregion of the base station exceeds the spreading factor or the FFT size.14. The base station of claim 8, wherein the mapping of the subcarrierscomprises mapping the subcarriers in a particular subband.
 15. A methodfor receiving control information by a terminal in an orthogonalfrequency division multiplexing (OFDM) system, the method comprising:receiving, by the terminal, information from a base station;demultiplexing, by the terminal, the received information to outputspread acknowledgement (ACK) information and other control information,the spread ACK information being mapped on subcarriers in a pattern forincreasing diversity gain of the spread ACK information; despreading, bythe terminal, the spread ACK information by applying a code from a setof codes; and decoding, by the terminal, the other control informationbased on a channel encoding scheme.
 16. The method of claim 15, whereinthe spread ACK information is mapped based on an ACK channel index. 17.The method of claim 15, wherein the spread ACK information is mapped toa plurality of OFDM symbols.
 18. The method of claim 15, wherein thespread ACK information is spread using a spreading factor.
 19. Themethod of claim 15, further comprising: receiving information through anACK channel corresponding to the ACK information allocated based on aspreading factor or a fast fourier transform (FFT) size.
 20. The methodof claim 19, wherein the ACK channel is allocated when a number ofterminals within a region of a base station exceeds the spreading factoror the FFT size.
 21. The method of claim 15, wherein the spread ACKinformation is mapped on the subcarriers in a particular subband.
 22. Aterminal for receiving control information in an orthogonal frequencydivision multiplexing (OFDM) system, the terminal comprising: atransceiver configured to receive information from a base station; and acontroller coupled with the transceiver and configured to: demultiplexthe received information to output spread acknowledgement (ACK)information and other control information, the spread ACK informationbeing mapped on subcarriers in a pattern for increasing diversity gainof the spread ACK information, despread the spread ACK information byapplying a code from a set of codes, and decode the other controlinformation based on a channel encoding scheme.
 23. The terminal ofclaim 22, wherein the spread ACK information is mapped based on an ACKchannel index.
 24. The terminal of claim 22, wherein the spread ACKinformation is mapped to a plurality of OFDM symbols.
 25. The terminalof claim 22, wherein the spread ACK information is spread using aspreading factor.
 26. The terminal of claim 22, wherein the controlleris further configured to receive information through an ACK channelcorresponding to the ACK information allocated based on a spreadingfactor or a fast fourier transform (FFT) size.
 27. The terminal of claim26, wherein the ACK channel is allocated when a number of terminalswithin a region of a base station exceeds the spreading factor or theFFT size.
 28. The terminal of claim 22, wherein the spread ACKinformation is mapped on the subcarriers in a particular subband.